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Diffstat (limited to 'src/ipa/libipa/lux.cpp')
| -rw-r--r-- | src/ipa/libipa/lux.cpp | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/src/ipa/libipa/lux.cpp b/src/ipa/libipa/lux.cpp new file mode 100644 index 00000000..bae8198f --- /dev/null +++ b/src/ipa/libipa/lux.cpp @@ -0,0 +1,181 @@ +/* SPDX-License-Identifier: BSD-2-Clause */ +/* + * Copyright (C) 2019, Raspberry Pi Ltd + * Copyright (C) 2024, Paul Elder <paul.elder@ideasonboard.com> + * + * Helper class that implements lux estimation + */ +#include "lux.h" + +#include <algorithm> +#include <chrono> + +#include <libcamera/base/log.h> + +#include "libcamera/internal/yaml_parser.h" + +#include "histogram.h" + +/** + * \file lux.h + * \brief Helper class that implements lux estimation + * + * Estimating the lux level of an image is a common operation that can for + * instance be used to adjust the target Y value in AGC or for Bayesian AWB + * estimation. + */ + +namespace libcamera { + +using namespace std::literals::chrono_literals; + +LOG_DEFINE_CATEGORY(Lux) + +namespace ipa { + +/** + * \class Lux + * \brief Class that implements lux estimation + * + * IPAs that wish to use lux estimation should create a Lux algorithm module + * that lightly wraps this module by providing the platform-specific luminance + * histogram. The Lux entry in the tuning file must then precede the algorithms + * that depend on the estimated lux value. + */ + +/** + * \var Lux::binSize_ + * \brief The maximum count of each bin + */ + +/** + * \var Lux::referenceExposureTime_ + * \brief The exposure time of the reference image, in microseconds + */ + +/** + * \var Lux::referenceAnalogueGain_ + * \brief The analogue gain of the reference image + */ + +/** + * \var Lux::referenceDigitalGain_ + * \brief The analogue gain of the reference image + */ + +/** + * \var Lux::referenceY_ + * \brief The measured luminance of the reference image, out of the bin size + * + * \sa binSize_ + */ + +/** + * \var Lux::referenceLux_ + * \brief The estimated lux level of the reference image + */ + +/** + * \brief Construct the Lux helper module + * \param[in] binSize The maximum count of each bin + */ +Lux::Lux(unsigned int binSize) + : binSize_(binSize) +{ +} + +/** + * \brief Parse tuning data + * \param[in] tuningData The YamlObject representing the tuning data + * + * This function parses yaml tuning data for the common Lux module. It requires + * reference exposure time, analogue gain, digital gain, and lux values. + * + * \code{.unparsed} + * algorithms: + * - Lux: + * referenceExposureTime: 10000 + * referenceAnalogueGain: 4.0 + * referenceDigitalGain: 1.0 + * referenceY: 12000 + * referenceLux: 1000 + * \endcode + * + * \return 0 on success or a negative error code + */ +int Lux::parseTuningData(const YamlObject &tuningData) +{ + auto value = tuningData["referenceExposureTime"].get<double>(); + if (!value) { + LOG(Lux, Error) << "Missing tuning parameter: " + << "'referenceExposureTime'"; + return -EINVAL; + } + referenceExposureTime_ = *value * 1.0us; + + value = tuningData["referenceAnalogueGain"].get<double>(); + if (!value) { + LOG(Lux, Error) << "Missing tuning parameter: " + << "'referenceAnalogueGain'"; + return -EINVAL; + } + referenceAnalogueGain_ = *value; + + value = tuningData["referenceDigitalGain"].get<double>(); + if (!value) { + LOG(Lux, Error) << "Missing tuning parameter: " + << "'referenceDigitalGain'"; + return -EINVAL; + } + referenceDigitalGain_ = *value; + + value = tuningData["referenceY"].get<double>(); + if (!value) { + LOG(Lux, Error) << "Missing tuning parameter: " + << "'referenceY'"; + return -EINVAL; + } + referenceY_ = *value; + + value = tuningData["referenceLux"].get<double>(); + if (!value) { + LOG(Lux, Error) << "Missing tuning parameter: " + << "'referenceLux'"; + return -EINVAL; + } + referenceLux_ = *value; + + return 0; +} + +/** + * \brief Estimate lux given runtime values + * \param[in] exposureTime Exposure time applied to the frame + * \param[in] aGain Analogue gain applied to the frame + * \param[in] dGain Digital gain applied to the frame + * \param[in] yHist Histogram from the ISP statistics + * + * Estimate the lux given the exposure time, gain, and histogram. + * + * \return Estimated lux value + */ +double Lux::estimateLux(utils::Duration exposureTime, + double aGain, double dGain, + const Histogram &yHist) const +{ + double currentY = yHist.interQuantileMean(0, 1); + double exposureTimeRatio = referenceExposureTime_ / exposureTime; + double aGainRatio = referenceAnalogueGain_ / aGain; + double dGainRatio = referenceDigitalGain_ / dGain; + double yRatio = currentY * (binSize_ / yHist.bins()) / referenceY_; + + double estimatedLux = exposureTimeRatio * aGainRatio * dGainRatio * + yRatio * referenceLux_; + + LOG(Lux, Debug) << "Estimated lux " << estimatedLux; + return estimatedLux; +} + +} /* namespace ipa */ + +} /* namespace libcamera */ |